Hi m8,

out of curiosity it may be worth checking fuel supply. Different car I know, but my mates Skyline was doing exact same thing as yours, and needed a fuel filter. Replaced filter, good supply and all was well with the world!

This wouldnt explain the misfire though - may be worth having it checked by a friendly local garage to ensure that it is not running lean, else small problem could become big problem!

Cheers

JJ